My L36 LIM Porting (with pics)...NOW WITH DATA! - Page 6 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-15-2007, 09:44 PM   #51
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That'* the one I used. The long straight one with the ROUNDED end. That way if you 'dig in' accidentally, it'* not a straight cut. Make sense?

These:







NOT anything like this:

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Old 03-15-2007, 10:02 PM   #52
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Default My L36 LIM Porting (with pics)

Will,

Makes absolute sense. Wondering if the diameter of those bits is good for the radius at the corners of the ports though.
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Old 03-15-2007, 10:09 PM   #53
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It'll get you VERY close.
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Old 04-04-2007, 03:19 AM   #54
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Spent the last week and a half tuning the stock 98 LeSabre with the DHP PowrTuner to get some baseline data. Installed the ported LIM yesterday, with no other changes apart from a Bill Buttermore sleeved EGR tube. Butt dyno said YESSSSS!!!!!!!!!!!!!!!

But I wanted some hard data....so I spent today doing a VE tune on the ported LIM. Here are the compared results:



As you can see, the Stock PCM "tune" is crap...in fact, the VE table is ď0.8í*Ē at all MAP and rpm values (GM must have laid off all the engineers in 1997).

On the stock LIM at 100kPa MAP, tuned VE peaked at 0.96 at 4000 rpm. After installing the ported LIM and re-doing the VE tune, VE at 100kPa MAP peaked at 1.01 at 4400 rpm (about a 5% increase in peak VE). Furthermore, the ported LIM was higher in VE at all engine speeds >=2400 rpm.

The torque peak appears to have shifted upward by some 400rpm. I would ballpark estimate an increase in torque of about 15-20 ft lb over stock, peaking at 4400rpm, and an increase of some 10-12 hp over stock, peaking at 5200rpm.


Not only that, but the ported LIM seems to have significantly reduced both the frequency and severity of KR. Looking back over the scans, and including only frames in fuel cells 2, 3 and 4 (i.e., accel only, no decel or idle), I did this analysis on KR:

Stock LIM:
Average 41% of frames with KR
Median KR value of 3.6 (in frames with KR)

Ported LIM:
Average 16% of frames with KR
Median KR value of 1.7 (in frames with KR)


These are some truly awesome results overall, and I am very happy with this $40 mod.

EDIT: For those coming late into this thread, bear in mind that this 98 L36 engine is bone stock, except for a 180 degree drilled t-stat.

EDIT 2: All tuning work was done at external temps 70-75 degrees F, and on the same driving route, trying to replicate each drive as closely as possible.
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Old 04-04-2007, 12:51 PM   #55
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Nice test, data and results.
Very concrete. I'm loving it.
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Old 04-04-2007, 01:03 PM   #56
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X2! That'* good info!
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Old 04-05-2007, 12:00 AM   #57
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Default My L36 LIM Porting (with pics)...NOW WITH DATA!

Great data AG. Glad it worked out. I should be on the road again soon.
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Old 04-05-2007, 12:06 AM   #58
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yeah thanks for the info
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Old 04-05-2007, 12:11 AM   #59
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That'* a significant change. Can you confirm you did no tuning between the LIM'*?

If so, this backs up the butt-dyno impressions from the first 2 test cars.
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Old 04-05-2007, 12:39 AM   #60
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Quote:
Originally Posted by willwren
That'* a significant change. Can you confirm you did no tuning between the LIM'*?

If so, this backs up the butt-dyno impressions from the first 2 test cars.
I did tune beyond the VE tune with the stock LIM (MAF, spark, etc.)...however, when I installed the ported LIM, I went back to the point where I finished the VE on the stock LIM and started over again from there.

Thus, the two "tuned VE" lines in the graph above are using identical, entirely stock tables for everything engine-related apart from the VE table itself (all Spark tables, Acceleration Enrichment, MAF--although the MAF sensor is unplugged during the VE tune, et.al.). They were done with PE set to 100% TP (i.e., there is no Performance Enrichment A/F "charge"). The tranny tables and fan settings were not entirely at stock settings, but they were identical between the two LIM tests.

I assure you, the differences I am seeing are ENTIRELY due to the porting of the LIM.

I'll be moving on to MAF tuning with the ported LIM next, and I expect to see little or no change to the MAF table values versus stock LIM...but I DO expect to hit higher MAF Hz values than I've hit before (if so, this would tend to confirm that I'm sucking more air).
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